I found some other interesting things playing around with my keyboards.
I swapped a few key caps from my Das 3 to the Filco (browns), and I find that they make a slightly different sound. I can't describe the difference, but they're just slightly different. Also, the Das' caps come off a lot easier on both keyboards. The Filco caps are tight on the Filco and I think even tighter on the Das. It's mostly in the cap moulding, but the key switches seem to make a slight difference too.
The keys are wobbly on the browns as I mentioned earlier. I find them relatively nice and tight on the blacks, and just now I see they're also tight on the blues. There doesn't seem to be much difference, but it's noticeable and it bothers me.
Back to key sound. Having had a few caps off, I really like the sound of rapid fire blues with the caps off. The Das' key caps really sharpen the click sound. If I could have the "bare sound" with caps on, that would be most awesome. There seem to be so many aspects to key sound. Without bottoming out (to eliminate one aspect): Every row of the Filco makes a different sound, so the board itself changes the sound. The key cap also changes the sound (re: the Das swap above - materials, and probably shape too). The mere presence of a key cap changes the key sound. I find the brown a little noisy too (since I bottom out a lot) - I bet if I stuck some damping material on the switch, I would make this so much quieter.
Having spent even more time with the keyboards, and reading a bit more here, I really should try the clear MX switches and perhaps even black alps to see how they compare. It's not going to happen for awhile though, since I can't find anyone close with other mech keyboards, and I need to space out my purchases. I'm now liking the blacks and blues over the brown. Poor brown, I seem to really bagging on it.

I think the biggest difference in feel is the tightness of the keys - If the browns were less wobbly, I would think better of them. Sigh.
Oh, almost forgot, my F, E, and Spacebar on the black are getting shinier. Why can't they make caps like they used to? Recalling by BTC keyboard - If they stuck that textured stuff that's over the lettering to completely cover the key, I bet they'll almost never go shiny unless you scraped it off. It was some durable stuff.